Big developments today in a storyline that has captivated Washington. Did Donald Trump's campaign collude with Russia ahead of last year's presidential election? Today, we learned of charges against two former campaign officials, and a third campaign adviser has pleaded guilty to lying to the FBI. NPR's Ryan Lucas has been following all this, and he's here with me now in the studio. Hey there, Ryan.

RYAN LUCAS, BYLINE: Hello.

KELLY: Give us some more detail on the charges against these ex-campaign aides.

LUCAS: Well, we have charges against a number of former Trump campaign figures. The first indictment came against Trump campaign chairman Paul Manafort and his business partner, Rick Gates. They face 12 counts, including conspiracy against the United States, conspiracy to launder money and making false statements. In short, basically, Manafort and Gates stand accused of running this kind of sprawling network of offshore bank accounts and shell companies to launder millions of dollars that they had earned from advising work that they did for a pro-Russian Ukrainian politician by the name of Viktor Yanukovych.

The indictment alleges that Gates and Manafort hid $75 million from the U.S. government. And the charges that they face, these are big charges, and they carry serious prison time. Manafort and Gates surrendered to the FBI this morning. They pleaded not guilty in federal court this afternoon. And that's big news.

KELLY: Absolutely. And meanwhile, it's not everything today. We mentioned this third campaign aide, George Papadopoulos. He pleaded guilty to lying to the FBI. What did he lie about? Who is he?

LUCAS: Well, according to court papers, Papadopoulos established a relationship with a professor in London in 2016. And this professor had significant ties to Russian government officials. And the professor told Papadopoulos in April of 2016 that the Russians had dirt on Hillary Clinton in the form of thousands of emails. Now, Papadopoulos also worked to try to set up a meeting between people in the Trump campaign and Russian officials, and he did this with the blessing of unnamed senior campaign officials.

KELLY: Now, George Papadopoulos is not a name familiar even to those of us who've tracked the Russia investigation really closely. Why is his guilty plea so important?

LUCAS: Well, it strikes at kind of the core mission, the main question of the Mueller probe, and that's possible ties between the Trump campaign and Russia. Now, Manafort and Gates's charges, they're related to work that they did in Ukraine starting in 2006. The indictment doesn't mention Russia's influence campaign during the 2016 election. The court papers for Papadopoulos, on the other hand, this is kind of the first time that we've seen in the special counsel's investigation the special counsel explicitly tie someone in the campaign to the Russians.

KELLY: And just to note in passing, Ryan, the timing. These papers dealing with Papadopoulos, they were unsealed today, but he was arrested back in July. He pleaded guilty October 5. It is kind of amazing that this has not leaked - we didn't hear about it until today.

LUCAS: It is. But special counsel Robert Mueller can keep a secret.

KELLY: (Laughter) So he says. All right. Papadopoulos has admitted lying to the FBI, as he said - as we've said. Is he now cooperating with investigators?

LUCAS: He is, yes. The court papers say that he's met with investigators several times since he was arrested. Part of the deal is that he continue to cooperate and provide information on matters that the government deems relevant. But also, remember that Papadopoulos isn't the only figure in kind of the Trump orbit who ostensibly had contacts with Russian officials.

KELLY: No.

LUCAS: You may recall that Attorney General Jeff Sessions and former national security adviser Michael Flynn did as well. And then don't forget this other lower-level campaign guy by the name of Carter Page. He did, too. Page came onboard as a foreign policy adviser to the campaign at the same time as Papadopoulos. He traveled to Moscow for a speech in the summer of 2016 and reportedly had meetings with government officials then.

KELLY: And real quick, how do you rate the possibility that the White House - which doesn't like any of these developments we're hearing about today - that the White House might take action against Bob Mueller?

LUCAS: It's certainly toyed with that idea. But from what we're hearing right now that's not something that the president is looking to do at the moment.

KELLY: At the moment. Watch this space. All right, NPR's Ryan Lucas, thanks a lot.